Reliable wireless transmission is difficult to achieve, since the time varying nature of multipath fading channels makes it a challenge when compared to communication over optical fibre, coaxial cable and copper twisted pair. Although an improvement in bit error rate (BER) can be achieved by increasing the power or bandwidth of transmitted signals, this would be contrary to the efficiency requirements of next generation wireless systems. Diversity schemes, based on multiple transmissions/receptions of data packets, have therefore been proposed as techniques to mitigate fading without increasing the transmitted power.
Prior diversity schemes have included frequency and time diversity. However, these approaches have the disadvantage that additional spectrum or time slots are used, thus reducing the overall system efficiency. On the other hand, space diversity, in which multiple transmit and receive antennas allow separation of received signals using spatial processing techniques, remains a possible alternative allowing improved overall economy and efficiency of a digital cellular system. Space diversity techniques based on multiple transmit and receive antennas are commonly referred to as MIMO (multi-input, multi-output) systems.
However, the various MIMO systems in existence typically trade off implementational simplicity against total achievable data rate. In other words, prior MIMO systems either achieve a high data rate at the expense of either high power consumption or high hardware complexity, or maintain low transmit power but provide a correspondingly low data rate. In either case, co-antenna interference (CAI) is the dominant limiting factor in achieving high data rates. This trade off is a drawback when designing for wireless transmission, since low power consumption and high data rate are both desirable. Hence, there is a need in the industry to provide a high-rate transmission and detection scheme, which can be implemented with relatively low complexity both at the transmitter and the receiver.